Many businesses incur significant expenditures for marketing activities in anticipation that such activities will increase revenue and promote growth of the business. Some of these expenditures can be associated with various forms of advertising media, such as television, radio, print (e.g., newspaper, magazine, catalog, direct mail, etc.), outdoor (e.g., billboard), in-store promotions, telephone solicitation, electronic mail, web-based ads, and so forth. The observed performance of certain marketing activities, such as cost per advertising impression, revenue per impression, and so forth, can be used to aid decisions regarding future expenditures. Accordingly, models can be developed for forecasting the financial future of various marketing activities based on historical data. In the context of online advertising, a so-called ad impression generally refers to an event where an online ad is displayed, regardless of whether it is clicked on or not. Thus, each time a given ad is displayed counts as one impression. Counting such ad impressions is a common approach by which most online advertising is assigned value (e.g., in currency), wherein the ad cost is quoted in cost per impression (CPI) or cost per 1,000 impressions (CPM).